[The expression of LINC00052 during glycidyl methacrylate-induced malignant transformation of 16HBE cells].

Objective: To investigate the expression and role of LINC00052 during glycidyl methacrylate (GMA) -induced malignant transformation of 16HBE cells. Methods: Human bronchial epithelial (16HBE) cells were divided into GMA transformation group and corresponding DMSO control group, and the 10th, 20th and 30th generation cells of each group were collected LncRNA microarrays were used to analysis expression of LINC00052 in different stage of malignant transformation. Bioinformatics analysis was applied and the relative expression of LINC00052 and its potentially target genes was detected by real-time quantification PCR (qPCR) . Results: The results of microarray analysis showed that LINC00052 was up-regulated by 1.32-fold, down-regulated by 1.64-fold and down-regulated by 4.92-fold in the malignant transformation early (P10) , middle term (P20) and late (P30) , respectively, The results of qPCR showed that compared with the DMSO control group, the expression of LINC00052 was up-regulated by 1.55 times, down-regulated by 1.20 times and down-regulated by 2.35 times in P10, P20 and P30, respectively, and the difference was statistically significant (P<0.05) . There was a statistically significant difference in the relative expression of NTRK3 between the GMA transformation group of P10 and P30 generations with the corresponding DMSO control group (P<0.05) . Conclusion: LINC00052 is highly expressed in early time of GMA-induced malignant transformation of 16HBE, and down-regulated in the middle and last stage of malignant transformation and may play a protective role in GMA-induced malignant transformation of 16HBE by influencing the expression of its target gene NTRK3.

[Correlation between FOXO3 gene polymorphisms and susceptibility to occupational noise-induced deafness].

Objective: To investigate the association between the single nucleotide polymorphisms of rs12212067 in FOXO3 gene and the susceptibility to occupational noise-induced deafness in a Chinese Han population. Methods: A total of 1 066 cases of noise exposure workers from a large chemical fiber factory in Jiangsu Province were selected as the study subjects. All subjects' basic data and field exposure data were collected through questionnaires and occupational health surveys. The subjects were divided into case group (531 persons, double ear high frequency average hearing threshold>25 dB) and control group (535 persons, double ear high frequency average hearing threshold≤25 dB) according to their results of pure tone hearing test .2ml fasting venous blood was collected for DNA extraction and genotyping was performed by TaqMan-PCR technique. Results: Genotyping results suggested that the GT+GG genotype is a risk factor for occupational noise-induced deafness, with an adjusted OR 95% confidence interval of 2.044 (1.51-2.78) . After the noise exposure intensity was stratified, the adjusted OR values and the 95% confidence intervals of noise intensity ≤85, 85-92 and>92 dB respectively 2.43 (1.52-3.90) , 2.17 (1.03-4.59) and 1.74 (1.07-2.83) . Conclusion: GT-GG genotype in rs12212067 of FOXO3 gene may be a risk factor for occupational noise-induced deafness.

Parametrically Tunable Soliton-Induced Resonant Radiation by Three-Wave Mixing.

We show that a temporal soliton can induce resonant radiation by three-wave mixing nonlinearities. This constitutes a new class of resonant radiation whose spectral positions are parametrically tunable. The experimental verification is done in a periodically poled lithium niobate crystal, where a femtosecond near-IR soliton is excited and resonant radiation waves are observed exactly at the calculated soliton phase-matching wavelengths via the sum- and difference-frequency generation nonlinearities. This extends the supercontinuum bandwidth well into the mid IR to span 550-5000 nm, and the mid-IR edge is parametrically tunable over 1000 nm by changing the three-wave mixing phase-matching condition. The results are important for the bright and broadband supercontinuum generation and for the frequency comb generation in quadratic nonlinear microresonators.

Higher risk for thyroid diseases in physicians than in the general population: a Taiwan nationwide population-based secondary analysis study.

BACKGROUND: Physicians have high work stress, responsibility for night shifts and chances of exposure to medical radiation, which may increase the risk for thyroid diseases. AIM: We conducted this study to assess the risk for thyroid diseases in physicians, which remain unclear. DESIGN: We used a secondary analysis of the Taiwan National Health Insurance Research Database for this study. METHODS: After excluding thyroid diseases occurring before 2006 and residents, physicians and general population were identified by matching with age and sex in 2009 in a 1:2 ratio. The risk for thyroid diseases was compared between the physicians and general population and among physicians by tracing their medical histories between 2006 and 2012. RESULTS: In total, 28,649 physicians and 57,298 general population were identified. Physicians had a higher risk for overall thyroid diseases than the general population [odds ratio (OR): 1.27; 95% confidence interval (CI): 1.10-1.47], including individual thyroid disease: thyroid cancer (OR: 1.89; 95% CI: 1.22-2.95), hypothyroidism (OR: 1.64; 95% CI: 1.23-2.18) and thyroiditis (OR: 1.48; 95% CI: 1.00-2.19). CONCLUSIONS: We showed that physicians had a significantly higher risk for thyroid diseases than the general population. This reminds us to pay more attention to thyroid diseases in physicians. Further studies about the underlying mechanisms are warranted.

The C-terminal cysteine of turbot Scophthalmus maximus translationally controlled tumour protein plays a key role in antioxidation and growth-promoting functions.

The translationally controlled tumour protein (TCTP) of turbot Scophthalmus maximus (SmTCTP) contains only one cysteine (Cys¹7°) at the C-terminal end. The biological role of this C-terminal Cys¹7° in the antioxidation and growth-promoting functions of SmTCTP was examined by site-directed mutation of C170A (Cys¹7° →Ala¹7°). It was found that C170A mutation not only obviously decreased the antioxidation capacity of the mutant-smtctp-transformed bacteria exposed to 0·22 mM hydrogen peroxide, but also significantly interrupted the normal growth and survival of the mutant-smtctp-transformed bacteria and flounder Paralichthys olivaceus gill (FG) cells, indicating a key role played by Cys¹7° in the antioxidation and growth-promoting functions of SmTCTP. This study also suggested that the self-dimerization or dimerization with other interacting proteins is critical to the growth-promoting function of SmTCTP.

Pretreatment with bilirubin protects islet against oxidative injury during isolation and purification.

BACKGROUND: A high yield of pure, viable islets is one of the most important prerequisites for successful islet transplantation. However, during isolation and purification, many factors may cause oxidative stress, impacting islet viability. Accumulating evidence indicates that bilirubin (BR) not only has antioxidative but also has cytoprotective activities. In this study, we investigated whether pretreatment with bilirubin would protect islets against oxidative damage during isolation and purification. METHODS: Wistar rats were randomly divided into control and BR groups. The latter rats received an injection of BR 2 hours before islet isolation, whereas the controls received vehicle. Islet purity was determined using a dithizone stain. Survival rate and viability were determined using acridine orange and propidium iodide staining and the Cell Counting Kit-8 Kit. Islet function was quantified by testing glucose-stimulated insulin secretion. Islet damage caused by oxidative stress was quantified by measuring the malondialdehyde (MDA) in freshly isolated islets. RESULTS: Pretreatment with bilirubin did not enhance the purity, but significantly enhanced the survival rate and viability of the islets. Islet function in the BR group was significantly better than that in the control cohort. The MDA level was 0.62 ± 0.23 nmol/L/µg protein in the BR group, which was significantly lower (P < .05) than that in controls (1.31 ± 0.34 nmol/L/µg protein). CONCLUSIONS: We concluded that oxidative stress during islet isolation and purification can be mitigated by BR pretreatment. BR exerts antioxidant and cytoprotective properties by reducing lipid peroxidation (MDA) and enhancing islet viability and function. Pretreatment with BR may become a simple, clinical applicable means to improve human islet isolation and transplantation outcomes.

Interrelationship between exposure to PCDD/Fs and hypertension in metabolic syndrome in Taiwanese living near a highly contaminated area.

Metabolic syndrome (MetS) consists of a constellation of metabolic abnormalities that confer increased risk of cardiovascular disease. There is a positive correlation between exposure to persistent organic pollutants and MetS. We examine the association between PCDD/Fs and MetS components in 1490 non-diabetic persons living near a highly dioxin-contaminated area. We used factor analysis, with a set of core variables considered central features of MetS and PCDD/Fs, to group similar risk factors. Serum PCDD/Fs were positively and significantly correlated with the number of MetS components. Four risk factors-lipidemia, blood pressure, body size, and glycemia-accounted for 72.6% of the variance in the 10 core factors, and PCDD/Fs were linked to MetS through shared correlations with high blood pressure. After adjusting for confounding factors, we found that diastolic blood pressure (ß=0.018; p=0.006), glucose (ß=0.013; p=0.046), and waist circumference (ß=0.721; p=0.042) significantly increased with increasing serum PCDD/F levels. We found significant trends for associations between metabolic syndrome and serum low-chlorinated PCDD/Fs. The highest quintiles of 2,3,4,7,8-PeCDF, 1,2,3,6,7,8-HxCDF and 2,3,7,8-TCDD had the top three adjusted ORs (95% CI) of 3.5 (1.9-6.3), 2.9 (1.7-4.9) and 2.8 (1.6-4.9), respectively. We also found a slight monotonic relationship between serum PCDD/Fs and the prevalence of MetS, especially when the serum dioxin level was higher than 25.4pg WHO(98)-TEQ(DF)g(-1) lipid (the fourth Quintile). We hypothesize that high-dose exposure to PCDD/Fs is a blood pressure-related factor that raises MetS risk.

The pharmacological effect of epinephrine administration via laryngeal mask airway in a porcine model of asphyxial cardiac arrest.

BACKGROUND: Earlier studies have shown that the laryngeal mask airway (LMA) is an effective alternative method for the administration of drugs. The pharmacological effect of drug administration via the LMA in cardiac arrest is still unknown. This study was designed to compare the effect of epinephrine administration tracheally or through the LMA in an asphyxial resuscitated porcine model. METHODS: Asphyxial cardiac arrest was initiated in 24 pigs, which remained untreated for 2 minutes. After 1 minute of basic life support cardiopulmonary resuscitation, the pigs were assigned to receive epinephrine (50 microg/kg) administration via one of three routes, either tracheally (group ET), from the upper end of the LMA (group LMA), or from a catheter inserted through the LMA into the trachea (group LMAC). Plasma epinephrine (PE) levels were taken before asphyxia and every 2 minutes after cardiac arrest was introduced. RESULTS: All animals had significant elevation of PE levels after the administration of epinephrine. The peak PE level was highest for group LMAC and lowest for group LMA. There were no significant differences between groups LMAC and ET. CONCLUSION: Drug administration from a catheter through the LMA into the trachea achieved comparable PE levels to those achieved by the tracheal route. Epinephrine administered via the LMA catheter may be an acceptable alternative to treat asphyxial cardiac arrest.

Etiology and outcome of patients presenting for poisoning to the emergency department in Taiwan: a prospective study.

Poisoning is one of the most common reasons for visiting the emergency department in many countries, and the pattern varies from countries to countries and time to time. To compare the etiology and outcome of poisoning patients in different gender and age groups, we conducted a prospective study at the emergency departments of two medical centers in southern Taiwan between January 2001 and December 2002. All cases of poisoning, excluding patients diagnosed as cases of alcohol or food poisoning, were included, and relevant information was collected. There were 1512 cases of poisoning observed with a male to female ratio of 1:1.2 (684/828). Overall, drugs (49.9%) were the main agents involved, and a suicidal attempt (66.1%) was the predominant etiology. A total of 63 fatalities (4.2%) were observed and pesticides, especially paraquat, resulted in most fatalities. Patients aged 19-30 years constituted the most cases, and significant differences in exposure agents, causes, and fatality rates were found among different age and gender groups. The results are compatible with the trend reported by other Asian countries. This study also shows important differences existing in poisoning patients of different age and gender groups. Therefore, different poisoning-prevention strategies should be applied to different groups.

Detection of oesophageal intubations using cuff pressures in a pig trachea oesophagus model.

BACKGROUND: The cuff pressures may be different in oesophageal and tracheal intubations. We conducted a study to evaluate if cuff pressures of endotracheal tubes (ETTs) could provide information to distinguish tracheal or oesophageal intubations in a pig trachea-oesophagus model. METHODS: In each preparation of pig trachea-oesophagus model, the trachea and the oesophagus were intubated separately with a cuffed ETT, and the cuff pressures were measured after each 1 ml increment of air (1-10 ml) during inflation. The cuff pressures and the pressure-volume relationships in both intubations were compared. RESULTS: The cuff pressures of oesophageal intubations were significantly higher than those of tracheal intubations in all comparisons from 1 to 10 ml of cuff volumes (P < 0.05). The cuff pressure-volume curve was steeper in the oesophageal intubation group, and the difference between the two curves was the largest when the cuff volume was 4-5 ml. CONCLUSIONS: We conclude that the cuff pressures may be useful in detecting oesophageal intubations. This method is faster than other confirmation measures as it can detect inadvertent oesophageal intubations at the time of inflating the cuffs.

Traumatic adrenal haematoma: a condition rarely recognised in the emergency department.

OBJECTIVE: To delineate the clinical features of traumatic adrenal haematoma, to help emergency physicians recognise the condition early and so to prevent adrenal crisis. METHODS: Review of the records of all patients admitted to Chi-Mei Medical Center, Tainan, Taiwan, with traumatic torso injuries, between 1 August 2003 and 31 August 2005. Of the 305 patients reviewed, 8 had adrenal haematoma. Injury Severity Scores, hospital course, need for intensive care unit admission and surgery or vascular embolisation, and concomitant injuries, were compared between patients with and without adrenal haematoma. RESULTS: No adrenal haematoma was recognised in the emergency department. No case of adrenal haematoma needed surgery or vascular embolisation, but each had associated injuries to other internal organs. All eight patients with, but only 106 patients without, adrenal haematoma sustained injuries to more than one internal organ (p<0.01). The mean Injury Severity Scores and lengths of hospital and intensive care unit stays among the two groups were not significantly different. There was no statistical significance in the differences in rates of admission to the intensive care unit, mortality, laparotomy or vascular embolisation between the two groups. CONCLUSIONS: Emergency physicians were liable in trauma cases to miss adrenal haematoma, which of itself was a benign condition but was associated with increased internal organ injuries and days in the intensive care unit. Emergency physicians should be aware of the possibility of adrenal haematoma in trauma cases in order not to miss the bilateral condition, which might lead to a deadly adrenal crisis.

Cancer risks in a population with prolonged low dose-rate gamma-radiation exposure in radiocontaminated buildings, 1983-2002.

PURPOSE: To assess cancer risks in a population that received prolonged low dose-rate gamma-irradiation for about 10 years as a result of occupying buildings containing 60Co-contaminated steel in Taiwan. MATERIALS AND METHODS: The cancer risks were compared with those populations with the same temporal and geographic characteristics in Taiwan by standardized incidence ratios (SIR), adjusted for age and gender. The association of cancer risks with excess cumulative exposure was further evaluated for their relative risks by the Poisson multiple regression analysis. RESULT: A total of 7271 people were registered as the exposed population, with 101,560 person-years at risk. The average excess cumulative exposure was approximately 47.8 mSv (range < 1 - 2,363 mSv). A total of 141 exposed subjects with various cancers were observed, while 95 developed leukemia or solid cancers after more than 2 or 10 years initial residence in contaminated buildings respectively. The SIR were significantly higher for all leukemia except chronic lymphocytic leukemia (n = 6, SIR = 3.6, 95% confidence interval [CI] 1.2 - 7.4) in men, and marginally significant for thyroid cancers (n = 6, SIR = 2.6, 95% CI 1.0 - 5.7) in women. On the other hand, all cancers combined, all solid cancers combined were shown to exhibit significant exposure-dependent increased risks in individuals with the initial exposure before the age of 30, but not beyond this age. CONCLUSIONS: The results suggest that prolonged low dose-rate radiation exposure appeared to increase risks of developing certain cancers in specific subgroups of this population in Taiwan.

The association between rainfall rate and occurrence of an enterovirus epidemic due to a contaminated well.

AIMS: To determine the association between rainfall rate and occurrence of enterovirus infection related to contamination of drinking water. METHODS AND RESULTS: One fatality case and three cases of severe illness were observed during the enterovirus epidemic in a village in southern Taiwan from 16 September to 3 October 1998. Groundwater samples were collected from the public well in the village after heavy rainfall to test for enterovirus using the reverse transcription-polymerase chain reaction (RT-PCR) assay. The RT-PCR assay detected the enterovirus in the groundwater sample collected on 26 September 1998. The logistic regression model also revealed a statistically significant association between the rainfall rate and the observation of cases of enterovirus infection. CONCLUSIONS: According to the fitted logistic regression model, the probability of detecting cases of enterovirus infection was greater than 50% at rainfall rates >31 mm h(-1). The higher the rainfall rate, the higher the probability of enterovirus epidemic. SIGNIFICANCE AND IMPACT OF THE STUDY: Contamination of drinking water by the enterovirus may lead to epidemics that cause deaths and severe illness, and such contamination may be caused by heavy rainfall. The major finding in this study is that the enterovirus could be flushed to groundwater in an unconfined aquifer after a heavy rainfall. This work allows for a warning level so that an action can be taken to minimize future outbreaks and so protect public health.

RANTES promoter polymorphism as a genetic risk factor for rheumatoid arthritis in the Chinese.

OBJECTIVES: There is increasing evidence suggesting a role of RANTES in the pathogenesis of rheumatoid arthritis (RA) and we evaluated the possible effect of RANTES gene on the susceptibility to RA in Chinese patients. METHODS: We examined the polymorphisms at the promoter positions -28 and -403 of this gene in 151 Chinese RA patients and 149 ethnically matched healthy controls. RESULTS: The genotypic frequencies in this study were in Hardy-Weinberg equilibrium. RA patients had significantly higher frequencies of the A allele (36.1% vs. 27.5%, p = 0.024) and A/A genotype (odds ratio [OR] = 3.3, 95% confidence interval [CI] = 1.4-7.9, p = 0.005) at the promoter -403 position. Differences in allele and genotype frequencies at the promoter -28 position between patients and controls were not statistically significant (for G allele, p = 0.103 and for genotype, p = 0.106). RA patients also had a significantly higher frequency of the -28 C/G with -403 A/A compound genotype (OR = 4.6, 95% CI = 1.5-14.5, p = 0.005), and a higher frequency of the -28 G/-403 A haplotype with marginal statistical significance (OR = 1.7, 95% CI = 1.0-3.1, p = 0.059). CONCLUSION: Our results indicate that polymorphism in the promoter region of RANTES gene is associated with the susceptibility to RA in the Chinese population.

Indicators of haemothorax in patients with spontaneous pneumothorax.

OBJECTIVES: To identify indicators and possible risk factors of haemothorax in patients with spontaneous pneumothorax. METHODS: All patients presenting to the emergency department of Chi-Mei Foundation Medical Center, Tainan, Taiwan with primary spontaneous pneumothorax between 1 January 1997 and 31 December 2002 were screened for inclusion in the present study. Of the 211 patients who qualified, eight had spontaneous haemopneumothorax (SHP) (3.79%). The clinical data and demographic characteristics of these patients were similar to those of patients with spontaneous pneumothorax without haemothorax (SP). RESULTS: All eight SHP patients were thin and young men (mean age 24 years and mean weight 56.1 kg). Seven were smokers. The patients with SHP were taller that the patients with SP (177.4 cm v 170.3 cm, respectively; p < 0.01), and tended to have a lower body mass index (BMI) (17.9 kg/m2 v 19.6 kg/m2, respectively; p = 0.06) and higher heart rate (101.0 v 88.0 beats/min, respectively; p = 0.09). Clinically, patients with SHP were more likely to have dyspnoea compared with SP patients (62.5% v 26.6%, respectively; p = 0.04) and lower levels of haemoglobin (12.8 v 14.7 g/dl, respectively; p = 0.01) and haematocrit (38.1% v 44.1%, respectively; p < 0.01). Chest x rays revealed pleural effusion in all patients with SHP but in none with SP. CONCLUSIONS: Patients with SHP are taller, with lower levels of haemoglobin and haematocrit, and are more likely to have dyspnoea than patients without haemothorax. The chest x ray finding of pneumothorax with an ipsilateral air-fluid level is a strong indicator of SHP.

Klebsiella pneumoniae fascial space infections of the head and neck in Taiwan: emphasis on diabetic patients and repetitive infections.

OBJECTIVES: To assess the epidemiological features, clinical characteristics, treatment, and outcome of head and neck infections caused by Klebsiella pneumoniae. METHODS: We reviewed records of four common aerobic pathogens isolated by the microbiological laboratory of a teaching hospital in Taiwan from July 1995 to December 1999. Patients aged 14 or older with community-acquired fascial space infections of head and neck were identified by review of medical records and included in the study. RESULTS: A total of 100 cases were identified, and K. pneumoniae was the most common pathogen of monomicrobial infections (48%), followed by viridans streptococci (15%). Polymicrobial infections were noted in 35 cases. In comparison with patients with infections not caused by K. pneumoniae, those with monomicrobial K. pneumoniae infections were older (P = 0.04) and had a higher prevalence of diabetes mellitus (P < 0.001), a longer duration of antimicrobial therapy (P = 0.007), a longer hospital stay (P = 0.001), and more repetitive infections (P = 0.001). All but one of K. pneumoniae isolates were susceptible to first generation cephalosporins and aminoglycosides. CONCLUSIONS: K. pneumoniae is an important endemic pathogen of fascial space infections of head and neck in Taiwan, especially among diabetics. Physicians should be aware of the tendency of this organism to cause repetitive infection.

Clinical significance and outcome of one or two rib lesions on bone scans in breast cancer patients without known metastases.

The presence of one or two rib lesions on bone scans of post-treatment breast cancer patients without known metastases often makes clinical decision making problematic. The aim of this study was to identify skeletal metastasis predictors that might help the management of these patients. We recruited post-treatment breast cancer patients without overt metastases whose bone scans showed (1) one or two rib hot spots, or (2) one rib lesion and a concurrent bone abnormality. Their clinical and serial scintigraphic data were collected, reviewed and evaluated for correlations. After their first abnormal bone scans, 23 patients (11 of the 77 patients initially with one rib lesion (incidence, 14.3%), three of the 27 patients with two rib lesions (incidence, 11.1%), and nine of the 11 patients with one rib lesion plus a concurrent bone abnormality (incidence, 81.8%)) developed multiple bone metastases within 2 years of the initial rib lesions in all but one case. Univariate analyses revealed that a concurrent bone lesion other than the rib, direct tumour invasion to the chest wall or skin, and 10 or more lymph nodes involved were associated with increased risks of bone metastases whereas longer persistence of the rib lesions was associated with a lower risk. Multivariate proportional hazard analyses indicated that patients with a concurrent bone lesion other than the rib (relative risk (RR)=39.65; 95% confidence interval (CI)=8.13-193.28), 10 or more lymph nodes involved (RR=13.49; 95% CI=2.09-86.91), and no radiotherapy (RR=7.59; 95% CI=2.11-27.39) were more likely to have bone metastases, while those with longer persistence of the rib lesions (RR=0.92; 95% CI=0.84-0.98) and longer time interval between surgery and the rib lesion detection (RR=0.96; 95% CI=0.94-0.99) were less likely. We have identified clinical features applicable to risk stratification. High incidence of bone metastases was noted in patients with one rib lesion and a concurrent bone abnormality. Regular follow-up for 2 years after detection of rib lesions is recommended, especially for those with risk factors.

Lipid peroxidation and cell death mechanisms in rats and human cells induced by chloral hydrate.

Chloral hydrate (CH) is widely used as a sedative and hypnotic in pediatric medicine. It is also a by-product of water chlorination and a metabolite of trichloroethylene. We examined the toxicological effects and cell death mechanisms of CH in rats and human Chang liver cells and lymphocytes. Monitoring of urinary 8-epi-PGF2alpha and serum levels of TNF-alpha served as index of lipid peroxidation and cytokine stimulation. The results indicated that a single intraperitoneal injection of 100 mg/kg CH in rats led to a nearly five-fold increase in urinary 8-epi-PGF2alpha on day 1, and a mild decrease on day 2 and day 3. The same treatment also induced significantly higher amounts of serum TNF-alpha on day 2 (about seven-fold). When the rats were treated with CH and vitamin E simultaneously, the amount of urinary 8-epi-PGF2alpha and serum TNF- were significantly lower than that in the rats treated with CH alone. CH caused a greater cytotoxic effect in human Chang liver cells than in comparison with lymphocytes. After treatment with CH, apoptosis features were observed in human lymphocytes, but not Chang liver cells. CH-induced cell damage in lymphocytes may offer signals for the induction of caspases activation. Further studies are needed to evaluate the relationship between caspases activation and the cleavage of other death substrates during postmitotic apoptosis in human lymphocytes.

Working hours spent on repeated activities and prevalence of back pain.

BACKGROUND AND AIMS: Back pain is the most common reason for filing workers' compensation claims in the United States and affects large numbers of workers in many other countries. To evaluate the associations between working hours spent on repeated activities and back pain, data gathered through the 1988 National Health Interview Survey were analysed. The data were also used to identify high risk occupations. METHODS: A total of 30 074 workers participated in the survey. They were asked to provide information on their job, including the time spent on repeated strenuous physical activities (RSPA) and the time spent on repeated bending, twisting, or reaching (RBTR) on a typical job. A case of back pain was defined as a worker who had back pain every day for a week or more during the past 12 months. Each case was asked to report the cause of back pain. Those who attributed their back pain to repeated activities (RA) or a single accident or injury (AI) were asked to recall whether they performed RA or had the AI at work. RESULTS: Whereas the prevalence of back pain increased as the number of working hours spent on RSPA or RBTR increased, the dose-response relations were not linear for either factor, suggesting the involvement of other unmeasured factors. The estimated overall prevalence of RA back pain was 8.9% among male workers and 5.9% among female workers. "Carpenters" had the highest prevalence (19.2%) and most cases (338 000) among the major occupations of men, and "nursing aides, orderlies, and attendants" had the highest prevalence (15.2%) and most cases (217 000) among the major occupations of women. CONCLUSIONS: The number of hours spent on repeated activities at work was associated with the prevalence of back pain. This study identified high risk occupations for future research and intervention.